Study On Absolute Stress Identification Method And Influencing Factors Of Steel Members Based On Ultrasonic Spectrum

The absolute stress of steel members in service is an index to judge whether the structure can serve normally.It is important to detect the absolute stress state of the steel members to master the structural safety performance,predict the service life of the structure,and determine the reinforcement of the structure.Compared to the traditional structure stress monitoring and stress detection methods,the ultrasonic method has the advantages of wide detection range,high detection efficiency and easy carrying of the device.The measurement result of the existing method based on TOF measurement is susceptible to environmental impact due to the testing process,and the device with high sampling rate is needed.Spectral analysis technology as an important means of signal analysis,can reflect the law of the ultrasonic frequency domain signal under the influence of absolute stress in steel members.Therefore,the method of identifying the absolute stress of steel members based on ultrasonic spectrum analysi s is presented in this paper.The main research contents are as follows:Establishment of absolute stress identification theory for steel members based on ultrasonic spectrum analysis.In this paper,a high frequency narrow pulse shear wave with wide band is chosen as the ultrasonic wave for detecting the absolute stress of steel members.Amplitude spectrum adjustment function is obtained by using the ultrasonic birefringence effect and the mathematical model.By discussing the characteristics of the amplitude spectrum adjustment function,the physical meaning of the birefringence function is defined and the expression of the characteristic parameters of the ultrasonic spectrum is determined.On the basis of those,the relationship between stress and ultraso nic spectral characteristic parameters is deduced by combining different types of ultrasonic acoustic formulas.Absolute stress identification and verification of steel members based on ultrasonic spectrum analysis.According to the ultrasonic characterist ics and theoretical deduction for the detectio n,the appropriate instrument is selected to combine and the signal data processing module is compiled to complete the absolute stress detection hardware system and software system based on ultrasonic spectrum analysis.According to the characteristics of selected ultrasonic and theoretical deduction,the appropriate detection instruments are selected to combine the detection system of absolute stress identification of steel members based on ultrasonic spectrum analysis.The correctness of the amplitude spectrum adjustment function is verified qualitatively,and the optimal polarization direction is determined by the optimal test of ultrasonic shear wave polarization direction.The relationship between the stress and the characteristic frequency of the ultrasonic spectrum is obtained by the calibration test.By using this relation formula,the detection for absolute stress of steel members is completed by utilizing the ultrasonic spectrum.And the error calculation is carried out to verify the feasibility of the detection method.Study on influencing factors of absolute stress identification of steel members based on ultrasonic spectrum analysis.The influence of the detection point on the detection results was stu died by experiment,and the stability of the detection method was evaluated.The thickness of the steel member was changed,and the influence of the thickness of the steel member on the detection sensitivity was analyzed.During the service stage,the steel members will be under different ambient temperature conditions.The absolute stress identification formula is deduced by considering the effect of temperature on the test results.The temperature effect coefficient is determined by the calibration experi ment,and the absolute stress of the steel member considering the temperature effect is detected by ultrasonic method.The strain gauge method is used to verify the detection result.At the same time,the reason why the ultrasonic signal reflected in the experiment is attenuated under high temperature is explored.